ST-LINK GDB Server issue with STM32C5

[AdrienST]

Hello, 

I'm using a NUCLEO-C5A3ZG. Not sure it's the right place to write but my goal is to setup the debugger using the STM32CubeCLT_1.21.0 Package under a VSCode environment (already using cortex-debug extension for other projects).

I am able to reach the target using the embedded stlink for example with a reading of the flash :

 /c/Program Files (x86)/ST/STM32CubeCLT_1.21.0/STM32CubeProgrammer
$ ./bin/STM32_Programmer_CLI.exe -c port=SWD freq=1000 mode=UR -r32 0x08000000 10
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.22.0
      -------------------------------------------------------------------

ST-LINK SN  : 005100353235511237333439
ST-LINK FW  : V3J17M10
Board       : NUCLEO-C5A3ZG
Voltage     : 3.29V
SWD freq    : 1000 KHz
Connect mode: Under Reset
Reset mode  : Hardware reset
Device ID   : 0x45A
Revision ID : Rev Z
Device name : STM32C59x/5A3
NVM size  : 1 MBytes
Device type : MCU
Device CPU  : Cortex-M33
BL Version  : 0x100
Debug in Low Power mode enabled


Reading 32-bit memory content
  Size          : 12 Bytes
  Address:      : 0x08000000
0x08000000 : 20000480 0800137D 080012B5

However when i try to use the GDB Server it fails with :

/c/Program Files (x86)/ST/STM32CubeCLT_1.21.0/STLink-gdb-server
$ ./bin/ST-LINK_gdbserver.exe --swd --halt -l 31


STMicroelectronics ST-LINK GDB server. Version 7.13.0
Copyright (c) 2026, STMicroelectronics. All rights reserved.

Starting server with the following options:
        Persistent Mode            : Disabled
        Logging Level              : 31
        Listen Port Number         : 61234
        Status Refresh Delay       : 15s
        Verbose Mode               : Disabled
        SWD Debug                  : Enabled

COM frequency = 24000 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 8000 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 3300 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 1000 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 200 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 50 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
COM frequency = 5 kHz
Target connection mode: Default
Target connection failed. Try connecting under reset
Target connection failed
Target unknown error 32

Error in initializing ST-LINK device.
Reason: Unknown. Please check power and cabling to target.

I tried in a linux environment, same behavior.

I checked the correct behavior on an other nucleo board NUCLEO-H7A3ZI & it is ok.

Thank's for your help.

[LaurentL · Accepted solution]

Hello,

This device has the CPU core on access port 1 so you should add "-m 1" in your args.

Rgds,

Laurent

[AdrienST]

Thank you very much !

Just for my understanding, as it's not a multicore device, what's the explanation for this change ?

[LaurentL]

Have a look in the Reference Manual on "Debug support (DBG)" chapter and then Access Ports :

There are two access ports (AP) attached to the DP.
• System debug access port (AP0): Enables access to the DBGMCU and the system ROM table via an APB bus.
• Cortex-M33 debug access port (AP1): Enables access to the debug and trace features integrated in the Cortex-M33 processor core via its internal AHB bus.